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Sanyang et al. (2017). “Tea tree fiber composites,” BioResources 12(2), 3751-3765. 3751

Tea Tree (Melaleuca alternifolia) Fiber as Novel Reinforcement Material for Sugar Palm Biopolymer Based Composite Films

Muhammed L. Sanyang,a Yokasundery Muniandy,b Salit M. Sapuan,a,b,* and Japar Sahari c

The tea tree (Melaleuca alternifolia) is well known for producing essential oil, which is used in medicinal and cosmetic products as a preservative, antiseptic, antibacterial, antifungal, and anti-pest additive. In this study, tea tree residues generated as agro-waste after the tea tree oil extraction process were utilized as cheap fiber material for the reinforcement of sugar palm starch (SPS)-based composite films. The crystallinity and functional groups of tea tree fiber (TTF) were investigated and the effect of TTF loading (0, 1, 3, 5, and 10 wt.%) on the tensile and morphological properties of TTF/SPS composite films were investigated. As the TTF loading increased from 0 to 10 wt.%, the tensile strength and modulus of TTF/SPS composite films were significantly increased, but their elongation at break declined. Optical microscopic and scanning electron microscopic images revealed that the TTF was randomly dispersed in all samples, and there was optimal compatibility between the fiber and matrix. Based on these findings, TTF can be considered as a potential reinforcement material for polymer composite films.

Keywords: Tea tree; Melaleuca alternifolia; Natural fibers; Sugar palm starch; Biocomposites

Contact information: a: Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest

Products, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; b: Department of

Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,

Malaysia; c:Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Jalan UMS, 88400

Kota Kinabalu, Sabah, Malaysia; *Corresponding author: [email protected]

INTRODUCTION

Biocomposites are widely used in the automotive, aerospace, packaging,

biomedical, construction, and furniture industries. Biopolymer composites reinforced

with natural fiber have gained attention due to their numerous advantages such as

affordability, renewability, abundance, environmental friendliness, aesthetics, ease of

handling, and an acceptable specific strength and stiffness (Sahari et al. 2012; Sanyang et

al. 2016a). The main purpose of developing green biocomposites is to replace the

available composites derived from metal, glass, ceramic, wood, and especially non-

biodegradable petroleum based plastics (Sain et al. 2005).

Recently, the use of biopolymers in the formulation of packaging films has

drastically accelerated. Starch is one of the most widely utilized biopolymers due to its

large availability, low cost, and environmental friendliness. Biodegradable films have

been prepared using starches from different sources such as cassava, potato, maize, corn,

sago, and rice (Sanyang et al. 2015a). Sugar palm starch is another potential biopolymer

for the development of biodegradable packaging films (Sahari et al. 2013a,b; Sanyang et

al. 2015a,b; 2016b). This starch is obtained from sugar palm trunk especially when the

tree is unproductive (Adawiyah et al. 2013). Sugar palm starch has been traditionally



used as a raw material for glue substances (Sahari et al. 2012). However, it has not yet

been developed into an industrial starch biopolymer.

Despite the many advantages associated with starch-based films, they mostly

demonstrate weak mechanical properties, which limit their effective application as a

packaging material. To address these hurdles, reinforcement materials such as natural

fibers or fillers have been incorporated in the starch matrix to enhance their functional

properties. Sahari et al. (2013a) reinforced plasticized sugar palm starch with different

sugar palm fiber loading. The mechanical and thermal properties of the sugar palm fiber

biocomposites reinforced by plasticized sugar palm starch significantly improved with an

increase in the loading of the fibers. Recently, Sanyang et al. (2016b) also reported the

effect of sugar palm cellulose in the enhancement of the tensile properties of sugar palm

starch-based biocomposite films. In this work, a novel natural fiber reinforcement

material (Melaleuca alternifolia (tea tree) fiber) was introduced into the sugar palm

starch matrix.

M. alternifolia has numerous oil constituents available in the leaf (Brophy and

Doran 1996). Although M. alternifolia is native to Australia, mainly found in Queensland

stretching to north-east New South Wales, it also extends to neighboring South East Asia

and the Pacific (Southwell and Lowe 1999). The Australian aborigines used ground tea

tree leaves for wound treatment due to the inherent antiseptic properties of the leaves.

They also use tea tree oil as a traditional medicine by inhaling the oils from crushed

leaves to treat colds and coughs; they treat skin infections by sprinkling the leaves after

applying a poultice (Shemesh and Mayo 1991). Additionally, tea tree leaves can be

soaked to make an infusion to treat sore throat and skin ailments. The volatile oil

constituents of M. alternifolia led to its commercial development as a medicinal and

aromatic plant. This aromatic and medicinal plant genus is popularly recognized for the

production of medicinal essential oils. In the form of a formulated or pure oil, tea tree is

widely utilized as a preservative, antiseptic, antibacterial, antifungal, or anti-pest additive

in an extensive range of medical and cosmetic products (Rodney et al. 2015a). These

products include shampoos, conditioners, soaps, bath oils, mouthwashes, toothpastes,

deodorants, moisturizers, face washes, foot sprays and powders, shaving products,

antiseptic creams, body lotions, sun blocks, lip balms, post-waxing treatments, and acne

creams as well as dog shampoos and veterinary care products (Wrigley and Fagg 1993;

Southwell and Lowe 1999; Rodney et al. 2015a).

Steam distillation is the most common method for tea tree oil extraction because it

causes minimum changes to the composition of the extract and because steam is readily

available, cheap, not chemically hazardous, can be used at low pressure, and can be

recycled (Davis 1999; Southwell and Lowe 1999). Steam distillation enables the aromatic

oil to be extracted at a constant, low temperature that does not damage the oil. In the late

1990s, tea tree essential oil experienced a multi-fold increase in production. During this

period, plantation production has risen from an insignificant contribution with respect to

bush production to being the predominant source of oil in Australia (Davis 1999; Rodney

et al. 2015a). With this development comes the issue of agro-waste from distilled tea tree

leaves/branches residue generated after the oil extraction process. High value can be

added to such agro-waste by utilizing it as a reinforcement or filler in polymer

composites. In this way, the potential environmental impact is averted, and the waste can

serve as a cheap reinforcement material to improve the properties of polymer composites.

Rodney et al. 2015b investigated the physical, chemical, and mechanical

properties of fibers obtained from different parts of the tea tree such as the trunk,



branches, and leaves. From their findings, tea tree trunk fibers manifested the highest

cellulose content, which in turn provided the highest tensile strength value compared to

their counterparts. Subsequently, Rodney et al. (2015c) utilized tea tree fibers as a

reinforcement or filler in tapioca starch composites. The incorporation of 5% tea tree

fiber in the tapioca starch matrix enhance the tensile strength of the biocomposite by

203.18% compared to the neat tapioca starch film. Hence, tea tree fibers can be

considered as potential reinforcement or filler for thermoplastic starch-based composites.

Nevertheless, there has been a limited amount of work done using tea tree fibers as a

potential reinforcement material in polymer composites. Therefore, the aim of this work

was to determine the effect of tea tree fiber loading on the mechanical properties of sugar

palm starch-based films.

EXPERIMENTAL

Preparation of Materials Tea tree fibers were taken from the Sabah Economic Development & Investment

Authority (SEDIA) tea tree field at the Demonstration Plot located at Mile 30 Kimanis,

Papar, Sabah, Malaysia. A chainsaw was used to cut down the tree for easy ground

harvesting of the fibers.

The fibers then were harvested manually using a knife. Fibers from different parts

of the tree such as leaves and twigs were extracted. The tea tree fibers were then dried.

The fibers remained unchanged during this process. Sugar palm starch and glycerol were

supplied by the Institute of Tropical Forestry and Forest Product (INTROP), University

Putra Malaysia.

Characterization of Tea Tree Fibers (TTF) Infrared (IR) analysis

The main functional groups of the fiber were determined by carrying out Fourier

transform infrared (FTIR) spectra analysis. The FTIR analysis was conducted at a

resolution of 2 cm-1 from 400 to 4000 cm-1. The sample was mixed with potassium

bromide (KBr) to obtain the fiber spectrum.

X-ray diffraction (XRD)

The crystalline structures of TTF were characterized by X-ray diffractometer

(APD2000, Italy) with Cu Kα radiation (λ=1.54 Å). The test was conducted under a

voltage of 40 kV and a current of 40 Ma. X-ray diffractograms of TTF were recorded for

2θ and the scanning region was between 5° to 40° at scan rate of 2° min-1. The

calculation for crystalline index of cellulose (CrI) for treated and untreated fiber was

determined based on Segal empirical method stated as follows (Eq. 1),

(1)

where I200 is the peak intensity corresponding to cellulose and Inon-Cr represents the non-

crystalline region.

𝐶𝑟𝐼 % = 𝐼200 − 𝐼𝑛𝑜𝑛 −𝐶𝑟

𝐼200 × 100%



Fabrication of the Biocomposites Tea tree fiber-reinforced SPS biocomposites were prepared by solution-casting

method (Sanyang et al. 2015a; 2015b; 2016b). Glycerol (G) was used as a plasticizer to

reduce the brittleness of SPS. Initially, 8% (w/w) aqueous dispersion of gelatinized sugar

palm starch was prepared by heating the film forming solution at 95 °C ± 2 °C. Prior to

their casting in glass Petri-dishes, the film forming solutions were cooled. The glass

Petri-dishes serving as a casting surface enabled the film to have a smooth and flat

surface. The freshly cast films were oven-dried at 40 °C to allow evaporation. After 24 h

of drying, films were peeled from the casting surface.

The method was repeated for the fabrication of sugar palm starch biocomposite

reinforced with tea tree fibers with different fiber contents (0, 1, 3, 5, and 10 wt.%)

(Sanyang et al. 2016b).

Mechanical Properties A tensile test was carried out in accordance with ASTM D882 (2002) with a

universal testing machine (Instron 3365, High Wycombe, England). The crosshead speed

was 2 mm/min. A total of 10 samples of 10 mm (W) x 70 mm (L) were tested for

different fiber loading biocomposite groups.

Optical Microscopy An Olympus SZX12 optical microscope (Tokyo, Japan) with a magnification of

7x was used to observe the transparency, porosity, and distribution of tea tree fibers in the

TTF/SPS composites. For an alternative view of the surface of tea tree fiber, a high-

resolution optical camera was also used for observation.

Scanning Electron Microscopy (SEM) Scanning electron microscopy (Hitachi S-3400N, Tokyo, Japan) with an operating

voltage of 5 kV was used to obtain scanning electron micrographs from the fractured

tensile test samples of the biocomposite. The homogeneous distribution of the fibers and

the matrix and the adhesion between them was evaluated.

RESULTS AND DISCUSSION Infrared (IR) analysis of TTF

Figure 1 presents the FTIR spectra of TTF. The broad absorption band at 3286.35

cm-1 is ascribed to the presence of O-H groups, which exist in cellulose, hemicellulose,

and lignin of the fiber. The peaks around 2921.14 cm-1 can be attributed to C-H stretching

vibration. Similar peaks were reported by Rodney et al. (2015c). The peak found at

1727.01 cm-1 is indicative of the existence of carbonyl groups (C=O) in the hemicellulose

and lignin, whereas the intensity peak around 1627 cm-1 is assigned to OH bending of

absorbed water within the fiber. In plane CH bending that may be from hemicellulose or

cellulose is characterized by the peaks around 1369 cm-1. Similar finding was reported by

Fan et al. (2012) while investigating the FTIR spectra of natural fibers.



Fig. 1. FTIR spectra of TTF

XRD of TTF XRD analysis was conducted to determine the crystallinity of TTF. Therefore,

high modulus fibers provide better mechanical strength when utilized as reinforcement

for polymer composites. The XRD diffractogram of TTF is shown in Fig. 2, where the

intensity of the diffraction peak can be clearly observed. The main diffraction peak at 2θ

(22.16º) represents a crystalline material which is believed to be the crystallographic

planes of cellulose I (I200). Another intensity peak appears near 2θ of 15.12°

corresponding to the crystalline phase of cellulose in TTF. On the other hand, the valley

shaped region between the two major peaks signifies the non-crystalline region of TTF,

which represents the amorphous materials in cellulose, hemicellulose, lignin and other

non-cellulose materials. Similar peaks were reported for raw sisal fibers and oil palm

empty fruit bunch by Kaushik et al. (2012) and Rayung et al. (2014), respectively. The

crystallinity index of TTF is calculated to be 43%. This value is higher than the

crystallinity index values reported by Edhirej et al. (2016) and Kaushik et al. (2012) for

cassava peel and sisal fiber, respectively. The obtained crystallinity index of TTF is also

higher than that of jute (34.3%), kenaf (34.9), and ramie fiber (34.8) reported by Poletto

et al. (2014).

Mechanical Properties Tensile strength

Figure 3 demonstrates the effect of fiber loading on the tensile properties of tea

tree fiber-reinforced sugar palm starch (TTF/SPS) biocomposite. The specimen with 10%

TTF/SPS content had the highest tensile strength value of 1.223 MPa, followed by 5%

TTF/SPS with 1.019 MPa, 3% TTF/SPS with 0.955 MPa, 1% TTF/SPS with 0.761 MPa,

and 0% TTF/SPS with 0.646 MPa. The increased tea tree fiber loading improved the



tensile strength compared with the neat plasticized SPS thin film by 17.80%, 47.83%,

57.74%, and 89.32% for 1, 3, 5, and 10 wt.% TTF loading, respectively.

Fig. 2. XRD of TTF

Fig. 3. Tensile strength of the tea tree fiber-reinforced SPS biocomposites



The low fiber loading in 1% TTF/SPS resulted in low tensile strength. This result

was attributed to there being insufficient fiber embedded in the SPS matrix to effectively

bear and transfer load to neighboring fibers. Thus, the tensile strength of TTF/SPS

biocomposites increased with increased tea tree fiber (TTF) loading. The addition of TTF

in SPS improved the mechanical strength of the biocomposite material. This result can be

attributed to the chemical similarities between the TTF and SPS, which provided good

compatibility and strong interfacial adhesion.

These results agree with the findings of many previous studies related to the use

of natural reinforcement materials for starch based composite films (Habibi et al. 2008;

Sahari et al. 2013a; Sanyang et al. 2016), which supports the observation that the

mechanical properties are strongly influenced by the fiber content in the matrix.

However, the tensile strength of samples with 5% TTF/SPS were significantly higher as

compared to 5% TTF reinforced tapioca starch composites reported by Rodney et al.

(2015c). Interestingly, 1% TTF/SPS composite films manifested higher tensile strength

value (0.95 MPa) than that of 5% TTF reinforced tapioca starch composites (0.5 MPa).

The wide variation in the tensile strength of this comparison can be attributed to the

superiority of SPS in film preparation over tapioca starch due to the high amylose content

in the native starch of the former as reported by Sanyang et al. (2016a).

Elongation at break (E%)

Figure 4 depicts the E% of TTF/SPS biocomposite films. The E% of TTF/SPS

biocomposites decreased as the loading of TTF increased from 0% to 10 %.

Fig. 4. Tensile at break (strain) of the biocomposite



The addition of the TTF made the E% of TTF/SPS biocomposites decrease from

28.6% to 15.4%. The highest value of elongation at break was observed for 0% TTF/SPS,

followed by 1%, 3%, 5%, and 10% TTF/SPS. After the addition of tea tree fiber increases

in the SPS matrix, the flexibility of the TTF/SPS composite films decreased by 25.89%,

38.05%, 35.53%, and 46.06% in 1, 3, 5, and 10 wt.% TTF/SPS, respectively.

These results showed that the 0% TTF/SPS biocomposite films were more

flexible than the other TTF/SPS biocomposite films. This effect was expected because

the incorporation of TTF imparts rigidity and restrains the mobility of the SPS molecules,

which lead to an inevitable decrease in the degree of the flexibility of the material.

Therefore, the films became less stretchable as their molecular mobility is interrupted by

the presence of the TTF. This result concurs with the findings of Sanyang et al. (2016b)

for sugar palm starch reinforced with sugar palm cellulose and Edhirej et al. (2016) for

bagasse-reinforced cassava starch composite.

Young’s modulus

Figure 5 shows that the 10% TTF/SPS composite had the highest tensile modulus

value of 30.50 MPa and also retained the highest stiffness properties. This was followed

by 5% TTF/SPS with 20.33 MPa, 3% TTF/SPS with 18.52 MPa, 1% TTF/SPS with 9.86

Mpa, and 0% TTF/SPS with 6.60 MPa.

Fig. 5. Young’s Modulus of the tea tree fiber-reinforced sugar palm starch biocomposite

The addition of 1, 3, 5, and 10 wt.% TTF improved the tensile modulus of the

neat SPS films by 49.39%, 180.62%, 209.10%, and 362.24%. These results explicitly

show that increasing the TTF loading from 1% to 10% led to an increase in the tensile

modulus of TTF/SPS composite films. This observed trend can be associated with the

weight percentage (wt%) increase of a high stiffness filler (TTF) loaded in a constant

weight low stiffness matrix (SPS). Hence, the stiffness of the TTF/SPS biocomposite

films significant increased. This result is similar to the previous studies carried out on the

loading effect of reinforcement material on the tensile modulus of SPS biocomposites

(Sahari et al. 2013a; Sanyang et al. 2016b).



The increase in tensile modulus of TTF/SPS biocomposite can also be attributed

to the stronger bonding between the SPS matrix and TTF fiber, which enhances the

interfacial adhesion between them, leading to a greater transfer of stress from the matrix

to the fibers during tensile testing. The tensile modulus of 5%TTF/SPS (20.33 MPa)

composite film is 5 times higher than that of 5 %TTF reinforced tapioca starch (4 MPa)

reported by Rodney et al. (2015c). Overall, the mechanical property results observed in

the study agreed with those reported by other researchers for natural fibers incorporated

in thermoplastic starches (Gáspár et al. 2005; Müller et al. 2009; Sanyang et al. 2016b;

Edhirej et al. 2016).

Optical Microscopy Figure 6 shows optical microscopic images that illustrate the dispersion of TTF in

the SPS matrix. More TTF were visible as the TTF loading increased from 1 to 10%. The

TTF were randomly dispersed in all samples with the exception of the 0% TTF control

film (Fig. 6a). The dispersion of TTF in 1%, 3%, and 5% TTF/SPS composites were

random with no significant agglomeration of TTF. However, the addition of 10% TTF

loading in the SPS matrix significantly increased the concentration of TTF in the

composite film, causing a slight degree of agglomeration, which should have affected

their tensile strength. On the contrary, the tensile strength of 10% TTF/SPS composite

films increased despite the slight aggregation of TTF. This can be attributed to the good

immersion of TTF in the SPS matrix as shown in Fig. 6e, which reflected optimal

compatibility between the fiber and matrix.

Scanning electron microscopy

Figure 7 (A-B) shows the plasticized SPS of the fractured portion after the tensile

test was performed. Figure 7 (C-D) shows the 1% TTF/SPS biocomposites. The interface

between fiber and matrix had poor bonding, as indicated by the wide gap between them.

The smooth fracture surfaces had a homogeneous matrix and good adhesion, which

improves the mechanical performance of biocomposites (Sahari et al. 2013b).

In both 0% and 1% TTF/SPS SEM micrographs, the smooth surface increase in

plasticized SPS was caused by the glycerol. At very low loading of fibers (0 and 1

w/w%), the specimens were very soft, homogeneous, and had smooth surfaces. At higher

fiber loading (3, 5, and 10 w/w %), the specimens were fragile, had rough surfaces, and

were very brittle.

Figure 7 (E-F) shows the fracture surface of biocomposites with 3% TTF (w/w%).

The adhesion in the interface of the fiber and matrix was indicated by the thin gap

between them, although voids still existed. The voids in the matrix loosened the fiber-

starch bond, and thus the stress was not transferred effectively to the whole composite.

This explains why 3% TTF/SPS exhibited a lower tensile strength as compared with 5%

and 10% TTF/SPS but was still higher than that of 0% plasticized SPS and 1% TTF/SPS.

The 5% TTF/SPS adhered well to the matrix even though small voids existed

(Fig. 7 (G-H)). This was due to the effect of TTF infiltration in the SPS matrix. Figure 7

also depicts fiber breakage, which indicates good adhesion of fiber-matrix interface when

subjected to tensile loading. Figure 7 (I-J) shows the 10% TTF/SPS biocomposite, where

the TTF adhered to the SPS matrix very well, and TTF was tightly bound to the matrix.

TTF embedded into the SPS matrix and the fiber surface was wetted by the SPS matrix,

which indicated the phase compatibility. This explains why 10% TTF/SPS exhibited the

highest tensile strength, as the bond between the fibers and the starch was strong.



Fig. 6. Image of surface morphology from optical microscopy 7x magnification of tea tree fiber reinforced with plasticized sugar palm starch (SPS) with (A) 0% TTF, (B) 1% TTF, (C) 3% TTF, (D) 5% TTF, and (E) 10% TTF





Fig. 7. Scanning electron micrographs of (A) 0%, (C) 1%, (E) 3%, (G) 5%, and (I) 10% with a plasticized SPS cross section of the fracture part after tensile; (B) 0%, (D) 1%, (F) 3%, (H) 5%, and (J) 10% are measures of thin film thickness

CONCLUSIONS

1. The FTIR and XRD results manifested that TTF is a potential reinforcement material

for SPS due to its OH groups, which can easily form hydrogen bonds with the SPS

molecules, whereas its moderate crystallinity is anticipated to generate good fiber

tensile strength, which in turn should enhance the mechanical properties of the

resulting composites.

2. TTF/SPS composite films at different fiber loading were successfully fabricated and

characterized.

3. All composites showed superior mechanical properties in comparison to neat SPS

films. Tensile strength and Young’s modulus were improved, while the tensile strain

decreased as the TTF (wt. %) increased.

4. SEM and optical microscopy studies showed a good dispersion of the tea tree fiber in

the matrix.



5. TTF can be effectively used as a reinforcement material in the development of anti-

pest biocomposites. It provides a cheap option for the development of green and

renewable biocomposites.

ACKNOWLEDGMENTS

The authors thank the Malaysia Ministry of Higher Education for financial

support through Research Acculturation Collaborative Effort (RACE) grant.

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DOI: 10.15376/biores.12.2.3751-3765

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